Hazardous rockslides have the potential to come crashing down on motorists at dozens of sites around O'ahu, including several on busy highways frequented daily by commuters, according to a much-anticipated Department of Transportation study released today.

State transportation officials released the study this morning to mark the end of an emergency rockslide prevention project at Makapu'u, which the study ranked as the most hazardous of its top 10 sites.

The Makapu'u project along Kalaniana'ole Highway was ranked just ahead of one near Waimea Bay on Kamehameha Highway across the bay from a site state officials fixed in the summer of 2000.

Eight other sites, including three within about three miles of each other outside Kailua on Pali Highway, need to be addressed, said Rod Haraga, director of the state Department of Transportation.

The problem sites are in communities all over the island: near Kahuku, near the Kipapa Gulch Bridge, two just north of Wahiawa and one right before Yokohama Bay.

And thousands of commuters regularly pass the three outside Kailua. There is one along the

offramp to Kane'ohe at Castle Junction, one near the old Kailua Drive-In on the Kailua-bound side of the Pali Highway, and one at the entrance to Kailua.

The $290,000 study evaulated more than 400 potentially hazardous sites. The study identified 66 slopes where potential for rockfall is high. With the report complete, the department will come up with a plan to deal with the potential roadside hazards, Haraga said.

"Once the plan is set, we will work as quickly as possible in constructing catchment devices to deal with the issue," Haraga said.

The department plans to set aside $1 million a year for design work on rockslide mitigation projects, Haraga said.

One of the first efforts will be to erect warning signs to alert motorists wherever a danger exists, Haraga said.

Haraga said a variety of factors will be used to decide which sites are addressed, including costs, availability of money, what kind of rock catchment system is needed and whether a detour road is available.

Because some of the problem sites are on private land, the state must work with each landowner to create a solution before anything can begin, he said.

"Some may take longer than others," Haraga said. "If we can get to one right away, we will do it real quick."

It is too early to know how much it will cost taxpayers to mitigate all the problem sites, he said.

"I wouldn't even want to guess right now," Haraga said.

The Makapu'u project, which cost $1.5 million, included the removal of loose rocks and debris and draping a wire mesh over the cliffs to contain falling rocks.

It was a safety concern that had worried residents for decades, but little was done until late last year. After an October 2002 rockslide sent debris from the cliffs onto the highway, blocking the road with what amounted to a truckload, transportation officials ordered work to begin three months ahead of schedule.